Problem 2909. Approximation of Pi (vector inputs)

Pi (divided by 4) can be approximated by the following infinite series:

pi/4 = 1 - 1/3 + 1/5 - 1/7 + ...

For a given number of terms (n), return the difference between the actual value of pi and this approximation of the constant.

This problem is the same as Problem 2908, except that the test suite will pass vectors for the number of terms, rather than breaking each truncated infinite series into a separate test.